Systems and methods for performing differential measurements in an electrical system
In accordance with the teachings described herein, systems and methods are provided for performing differential measurements in an electrical system. A first meter may be used that has a first time reference. A second meter may be used that has a second time reference, wherein the second time reference is synchronous with the first time reference. The first and second meters may be configured to use the first and second time references, respectively, to take time synchronized measurements of the electrical system. A processor may be used to receive the time synchronized measurements from the first and second meters and compare the time synchronized measurements to determine one or more electrical characteristics of the electrical system. The processor may also be used to correct for any existence time variation between the time synchronized measurements.
This technology relates generally to the measurement and analysis of electrical systems.
BACKGROUND AND SUMMARYThe characteristics of an electrical system can often be better analyzed if measurements are available from multiple points within the system. For example, electrical characteristics of a component in a power distribution system (e.g., distribution impedance, power loss, power delivery efficiency, etc.) may be determined by comparing measurements taken at the source and load ends of the component. However, to accurately calculate a differential measurement in a dynamic system, the measurements being compared should be synchronous.
In accordance with the teachings described herein, systems and methods are provided for performing differential measurements in an electrical system. A first meter may be used that has a first time reference. A second meter may be used that has a second time reference, wherein the second time reference is synchronous with the first time reference. The first and second meters may be configured to use the first and second time references, respectively, to take time synchronized measurements of the electrical system. A processor may be used to receive the time synchronized measurements from the first and second meters and compare the time synchronized measurements to determine one or more electrical characteristics of the electrical system. The processor may also be used to correct for any existent time variation between the time synchronized measurements.
BRIEF DESCRIPTION OF THE DRAWINGS
In the illustrated example, the first meter 14 is attached to one or more conductors at a first location (Point A) in an electrical distribution system 12. The second meter 16 is attached to the same conductor(s) at a second location (Point B) in the electrical distribution system 12. Time synchronized measurements are then taken at the two locations (Points A & B) by the respective meters 14, 16, and the measurements are provided to a processor 18. In addition, the measurements may be time referenced by including a time-stamp or other indication of the time at which the measurement was taken.
The processor 18 receives the measurements from the meters 14, 16 and performs differential calculations using the measurements to determine electrical parameters between the two locations (Points A & B) in the distribution system 12. For example, the processor 18 may use the measurements to determine the distribution impedance (Z), the voltage drop, the line current, the power loss, the power delivery efficiency, and/or other electrical parameters. Other, higher-order parameters may also be determined using the resultant differential measurements.
The processor 18 may be located remotely from the time synchronized meters 14, 16, as illustrated in
As illustrated in
In one example, the time references for the meters 14, 16 may be synchronized by aligning a time reference, such as a clock, in each meter 14, 16 with a common trusted time reference. For instance, internal clocks in the meters 14, 16 may be aligned with an atomic clock, a satellite clock, the cycles of a synchronous waveform (e.g., a 60 Hz power transmission) or some other trusted time reference. In another example, the meters 14, 16 may use the 60 Hz cycles of a power distribution system as their time reference instead of utilizing an internal clock.
If the meters 14, 16 include time references that are sufficiently synchronized and that do not drift a meaningful amount during measurements, then no further time synchronization may be necessary. This may be the case if the meters 14, 16 include accurate clocks that are capable of being synchronized to a sufficiently fine resolution. In another example, sufficient time synchronization may be maintained between the meters by synchronizing them on an ongoing basis, for instance by receiving occasional precise synchronizing signals from an external signal (e.g., a satellite), or some other suitable means. If a sufficient level of time synchronization between the meters 14, 16 cannot otherwise be obtained, however, then the processor 18 may utilize cross-correlation algorithms to further time synchronize the measured data, as illustrated in
With reference again to
The amplitudes of the measurements should also be calibrated so that measurements of the same signal at the same point in the system will be substantially identical on both meters 14, 16. If the amplitude calibrations of the meters 14, 16 are sufficiently accurate, and these calibrations do not drift by a meaningful amount, then no further amplitude synchronization may be necessary to perform differential calculations. This may be the case, for example, if very accurate meters are utilized that have been previously calibrated to a sufficiently fine resolution, such that the measurements of each meter 14, 16 are substantially identical. If this level of calibration is not present in the meters, however, then further amplitude synchronization may be performed.
As shown in
As illustrated in
This written description uses examples to disclose the invention, including the best mode, and also to enable a person skilled in the art to make and use the invention. The patentable scope of the invention may include other examples that occur to those skilled in the art.
Claims
1. A system for performing differential measurements in an electrical system, comprising:
- a first meter having a first time reference;
- a second meter having a second time reference, the second time reference being synchronous with the first time reference;
- the first and second meters being configured to use the first and second time references, respectively, to take time synchronized measurements of the electrical system; and
- a processor that receives the time synchronized measurements from the first and second meters and compares the time synchronized measurements to determine one or more electrical characteristics of the electrical system,
- the processor being further configured to correct for time variation between the time synchronized measurements.
2. The system of claim 1, wherein the first and second time references are internal clocks.
3. The system of claim 1, wherein the processor is located remotely from the first and second meter.
4. The system of claim 3, wherein the processor receives the time synchronized measurements over a wireless communication link.
5. The system of claim 3, wherein the processor receives the time synchronized measurements over a wired communication link.
6. The system of claim 3, wherein the processor receives the time synchronized measurements using one or more transferable data storage devices.
7. The system of claim 1, wherein the processor is resident in at least one of the first and second meters.
8. The system of claim 1, wherein the processor corrects for time variation by performing a cross-correlation function with respect to the time synchronized measurements.
9. The system of claim 1, wherein the time synchronized measurements each identify the time at which the time synchronized measurement was taken.
10. The system of claim 1, wherein the time synchronized measurements include at least one of impedance measurements, voltage measurements, current measurements or power measurements.
11. The system of claim 1, wherein the one or more electrical characteristics are compared with one or more expected values.
12. The system of claim 1, wherein the electrical system is a power distribution network.
13. The system of claim 1, wherein the time synchronized measurements are taken at multiple locations in the electrical system.
14. The system of claim 13, wherein the time synchronized measurements are used to identify one or more electrical characteristics of a plurality of component elements in the electrical system.
15. The system of claim 13, wherein the time synchronized measurements are used to identify a faulty component in the electrical system.
16. The system of claim 13, wherein the time synchronized measurements are used to identify arc flash potential at a plurality of locations in the electrical system.
17. The system of claim 13, wherein the electrical system is an uninterruptible power supply system.
18. The system of claim 1, wherein the time synchronized measurements are used to evaluate electrical characteristics of a power transforming component in the electrical system.
19. A method for measuring one or more electrical characteristics of an electrical system, comprising:
- synchronizing a first time reference for a first meter with a second time reference for a second meter;
- using the first meter to measure one or more electrical characteristics at a first point in the electrical system to generate a first time-synchronized measurement;
- using the second meter to measure the one or more electrical characteristics at a second point in the electrical system to generate a second time-synchronized measurement;
- transferring the first time-synchronized measurement and the second time-synchronized measurement to a processor;
- correcting for any existent time variation between the first time-synchronized measurement and the second time-synchronized measurement; and
- comparing the first time-synchronized measurement with the second time-synchronized measurement to determine a differential electrical characteristic between the first point and the second point in the electrical system.
20. The method of claim 19, wherein the correction of any existent time variation is performed using a cross-correlation function.
21. The method of claim 19, further comprising:
- using the first meter to measure the one or more electrical characteristics at the first point in the electrical system to generate a third time-synchronized measurement
- using the second meter to measure the one or more electrical characteristics at a third point in the electrical system to generate a fourth time-synchronized measurement;
- transferring the third and fourth time-synchronized measurements to the processor;
- comparing the third time-synchronized measurement with the fourth time-synchronized measurement to determine a second differential electrical characteristic; and
- comparing the differential characteristic with the second differential characteristic to determine electrical characteristics of two or more components of the electrical system.
22. The method of claim 21, further comprising:
- comparing the electrical characteristics of the two or more components to isolate a component of the electrical system that is not operating correctly.
23. The method of claim 21, further comprising:
- using the electrical characteristics of the two or more components to determine an arc flash potential associated with each of the two or more components.
24. A measurement system for an electrical system, comprising:
- a first meter having a first time reference;
- a second meter having a second time reference, the second time reference being synchronous with the first time reference;
- the first and second meters being configured to use the first and second time references, respectively, to take time synchronized measurements at two or more points in the electrical system.
- means for correcting for any existent time variation between the time synchronized measurements; and
- means for comparing the time synchronized measurements to determine one or more differential electrical characteristic between the two or more points in the electrical system.
Type: Application
Filed: Sep 8, 2006
Publication Date: May 17, 2007
Inventors: Robert Moore (San Jose, CA), Kennebec Kious (Walnut Creek, CA)
Application Number: 11/517,671
International Classification: G01R 31/08 (20060101); G08B 21/00 (20060101);